Such a device is known in the field, for instance from European patent application EP 1647666 of the same applicant.
The known device simplifies assembly due to the releasable fastening of the raising cords to the winding rollers but has the drawback that in the case of a plurality of winding rollers mutual alignment thereof is necessary prior to passing the shaft therethrough. Once the shaft has been passed through the winding rollers, the winding rollers must then be mounted fixedly on the shaft in order to make the device ready for use.